MacBook Pro - reliable, fast storage?

Hello all,
I recently bought a Macbook pro with a 120 GB 5400 rpm HDD. I do a lot of audio editing and anticipate that I will need to increase my storage pretty soon. I am confused about what solution to go with, so am seeking advice in this from.

1. Increase the internal drive to a 200 GB 7200 rpm (expensive, maxes out at 200 GB so I might have to rule out this option)
2. Add an external drive via firewire 800 port
3. Use an external drive via a ExpressCard Serial ATA/eSATA adapter